Common use of For actual ROAE and Simple Average Clause in Contracts

For actual ROAE and Simple Average. Net Income Growth numbers between the numbers on the matrix, the Committee will interpolate to arrive at the earned award. 3.) For purposes of the Award, the “TSR” for the Relative 3-year TSR for the Company and each of its Peer Group Members for the Performance Period will be determined by comparing the average closing price for a share of common stock of each company during the period beginning 10 days prior to the end of the Performance Period and ending 10 days after the Performance Period plus the cumulative dividends earned during the Performance Period, to the average closing price of a share of common stock of each company during the period beginning 10 days prior to the start of the Performance Period and ending 10 days after the start of the Performance Period. Relative 3 Year TSR vs. Peers 1st 200% 2nd 180% 3rd 160% 4th 140% 5th 120% 6th 100% 7th 85% 8th 70% 9th 55% 10th 40% 11th 25% 12th 10% 13th —% Exhibit 99.1 ADDENDUM B NorthWestern Energy Peer Companies*

For actual ROAE and Simple Average. Net Income Growth numbers between the numbers on the matrix, the Committee will interpolate to arrive at the earned award. 3.) For purposes of the Award, the “TSR” for the Relative 3-year TSR for the Company and each of its Peer Group Members for the Performance Period will be determined by comparing the average closing price for a share of common stock of each company during the period beginning 10 days prior to the end of the Performance Period and ending 10 days after the Performance Period plus the cumulative dividends earned during the Performance Period, to the average closing price of a share of common stock of each company during the period beginning 10 days prior to the start of the Performance Period and ending 10 days after the start of the Performance Period. Relative 3 Year TSR vs. Peers 1st 200% 2nd 180200% 3rd 160200% 4th 140150% 5th 120150% 6th 150% 7th 100% 7th 85% 8th 7075% 9th 5575% 10th 4075% 11th 25% 12th 1025% 13th —% Exhibit 99.1 ADDENDUM B NorthWestern Energy Peer Companies*